Check valve



FIG. 1 is a perspective view of check valve showing my new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a rear elevational view thereof;

FIG. 4 is a left side elevational view thereof;

FIG. 5 is a right side elevational view thereof;

FIG. 6 is a top side elevational view thereof; and,

FIG. 7 is a bottom side elevational view thereof. 

The ornamental design for check valve, as shown and described. 